Chiefs’ Inquiry Corner-6/13/22

June 13, 2022

Chief residents of the NYU Langone Internal Medicine Residency give quick-and-easy, evidence-based answers to interesting questions posed by house staff, both in their clinics and on the wards.

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 Antithrombin deficiency is a type of clotting disorder characterized by deficiency of antithrombin III (better known as antithrombin), an inhibitor of several enzymes in the coagulation system, including factor IIa (thrombin), IXa, Xa, and XIIa, predisposing patients to an increased risk of venous thrombosis and even (although much less commonly) arterial thrombosis. This disorder may be inherited or acquired (e.g., in people with severe liver disease [as antithrombin is synthesized in the liver] or nephrotic syndrome [due to loss of antithrombin in the urine]). Treatment of clots caused by antithrombin deficiency requires special consideration- people with this disorder usually do not respond to heparin therapy, since heparin exerts its effects by forming a complex with antithrombin molecules and then will subsequently inactivate thrombin, activated Xa, and other activated clotting factors; a reduced amount of antithrombin available will result in reduced response to heparin. Instead, treatment with a direct thrombin inhibitor, such as argatroban or dabigatran is recommended. In certain situations, there may be a role for antithrombin replacement in people with a known history of antithrombin deficiency (such as a planned major operation or acute severe trauma).

References:  Antithrombin Deficiency
 Generally, the common bile duct is considered to be dilated when it is 7mm or greater in diameter on ultrasound, or 10mm or greater in diameter on CT scan. If the patient has clinical or laboratory findings concerning for obstruction, then further workup is warranted with ERCP, MRCP, or endoscopic ultrasound (EUS) depending on the specific clinical context. (Of note, such concerning clinical findings include jaundice, pruritus, weight loss [concerning for malignancy], fever, and right upper quadrant abdominal pain; concerning laboratory findings include elevations in AST, ALT, alkaline phosphatase, and/or bilirubins). Additional ‘red flags’ that would indicate further workup is necessary include a concurrently dilated pancreatic duct, moderate-to-severe extrahepatic duct dilation (10mm or greater in diameter), and new or progressive dilation when compared to prior imaging. In the absence of these aforementioned concerning findings, the patient should be assessed for risk factors for nonobstructive dilation, including age >60, opioid use, history of cholecystectomy or choledochal cysts. If they have such risk factors, then typically, no further workup is indicated. If they do not have such risk factors, then MRCP or EUS would still be indicated to further evaluate the incidentally dilated common bile duct.

References: Does incidentally detected common bile duct dilation need evaluation?
 Carnett’s sign is a physical exam maneuver that can be utilized in someone with abdominal pain to help distinguish between abdominal wall (somatic) pain and pain of the organs underneath the abdominal wall (visceral pain). The examiner presses the point of maximal abdominal tenderness with the patient in the supine position, and asks the patient to raise their head and shoulders from the examination table, or, alternatively to lift both legs with straightened knees (both of which leads to tensing of the abdominal wall). Carnett’s sign is considered positive when the abdominal tenderness either does not change or increases, and indicates the source of abdominal pain is the abdominal wall itself (for example, due to hernias, nerve entrapment syndromes, or myofascial pain). A negative Carnett’s sign occurs when the abdominal tenderness decreases, and suggests the source of the pain is intra-abdominal. Sensitivity of this exam maneuver is 78% and specificity is 88% in detecting abdominal wall pain, and can be useful in the evaluation of patients presenting with abdominal pain as it encourages the clinician to include diagnoses other than intra-abdominal etiologies on the differential. 

References: Diagnostic Effect of Consultation Referral from Gastroenterologists to Generalists in Patients with Undiagnosed Chronic Abdominal Pain: A Retrospective Study